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Carl B

Carl Borrebaeck

Professor

Carl B

Escherichia coli TolA tolerates multiple amino-acid substitutions as revealed by screening randomized variants for membrane integrity and phage receptor function

Author

  • Fredrik Karlsson
  • Ann-Christin Malmborg Hager
  • Carl Borrebaeck

Summary, in English

Escherichia coli TolA is a cytoplasmic membrane protein required for outer membrane integrity and the translocation of F-specific filamentous (Ff) bacteriophage DNA. Both phage infection and membrane integrity depend on several TolA interactions, e.g. those of the TolA C-terminal domain (TolAIII). Membrane integrity involves interaction with two host proteins and phage translocation requires direct interaction with the N-terminal domain (N1) of Ff phage protein g3p. Although cocrystallization of TolAIII and N1g3p has identified several contact points, it is still uncertain which residues are selectively involved in the different TolA functions. Thus, four different limited substitution libraries of TolA were created, targeting contacts at positions 415-420. These libraries were introduced into the tolA strain K17DE3tolA/F+ and several variants, containing complementing, multiple amino-acid substitutions, were identified. However, most randomized variants did not complement the tolA strain K17DE3tolA/F+. The TolA variants that restored sensitivity to phage infection displayed a considerable sequence variation, while the few variants that restored tolerance to detergent were from the same library. A comparison of the generated residue variation and natural variation, suggests that structural dependence overrides contact residue dependence. Thus, library screening can be efficient in identifying TolA variants with different functionally associated characteristics.

Department/s

  • Department of Immunotechnology

Publishing year

2006

Language

English

Pages

81-88

Publication/Series

FEMS Microbiology Letters

Volume

259

Issue

1

Document type

Journal article

Publisher

Oxford University Press

Topic

  • Immunology in the medical area

Keywords

  • functional screening
  • randomized TolA
  • Escherichia coli

Status

Published

ISBN/ISSN/Other

  • ISSN: 1574-6968